U.S. patent application number 11/203106 was filed with the patent office on 2006-03-16 for relay node installation selection method, relay node installation point selection device, same device-mounted base station, and program product for executing same selection method.
This patent application is currently assigned to NEC CORPORATION. Invention is credited to Takahiro Ookuma.
Application Number | 20060056329 11/203106 |
Document ID | / |
Family ID | 36033791 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060056329 |
Kind Code |
A1 |
Ookuma; Takahiro |
March 16, 2006 |
Relay node installation selection method, relay node installation
point selection device, same device-mounted base station, and
program product for executing same selection method
Abstract
In a wireless multi-hop network, a node directly connectable in
one hop at a relay node installation point candidate is detected.
When a node-to-node connectability diagnosis result demonstrates
that an isolated node exists, the candidate enabling a connection
to the base station and yet the candidate enabling a one-hop
connection to the isolated node is selected as a relay node. When
an isolated node still remains, the candidate enabling one-hop
connections both to the remaining isolated node and to the isolated
node that has newly become connectable to the base station is
additionally selected as a relay node from among candidates that do
not enable a connection to the base station. The route of "the
remaining isolated node>additionally added relay
node>isolated node that has become connectable to the base
station>base station" is established.
Inventors: |
Ookuma; Takahiro; (Tokyo,
JP) |
Correspondence
Address: |
YOUNG & THOMPSON
745 SOUTH 23RD STREET
2ND FLOOR
ARLINGTON
VA
22202
US
|
Assignee: |
NEC CORPORATION
TOKYO
JP
|
Family ID: |
36033791 |
Appl. No.: |
11/203106 |
Filed: |
August 15, 2005 |
Current U.S.
Class: |
370/315 |
Current CPC
Class: |
H04B 7/155 20130101;
H04W 16/18 20130101; H04W 24/02 20130101 |
Class at
Publication: |
370/315 |
International
Class: |
H04B 7/14 20060101
H04B007/14 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2004 |
JP |
2004-265324 |
Claims
1. A method for selecting a relay node installation point used for
forming a route between a base station and an isolated node in a
wireless multi-hop network from among predetermined relay node
installation point candidates, comprising the steps of: a first
step for receiving a node-to-node connectability diagnosis result
by said base station; a second step for, for each of said relay
node installation point candidates, receiving a detection result of
a node to which a direct connection is enabled by each relay node
installation point candidate; and a third step for, when it has
been judged that there exists the isolated node, selecting a relay
node installation point a connectable to said base station and a
directly connectable to an isolated node as an installation point
based on said detection result of said second step.
2. The method according to claim 1, said method further comprising
a fourth step, said fourth step being a step for, when there still
remains the isolated node unconnectable to said base station after
said third step ends, selecting the relay node installation point
enabling a direct connection to both the remaining isolated node
and the isolated node that has become connectable to said base
station as a result of said third step from relay node installation
point candidates that do not enable a connection to said base
station as a relay node installation point based on said detection
result.
3. The method according to claim 2, wherein when there still
remains the isolated node unconnectable to said base station even
after said fourth step, said method further repeats said fourth
step.
4. The method according to claim 1, said method further comprising
a fifth step for calculating a duplication quantity indicating the
number of relay node installation point candidates to which the
isolated node is directly connectable based on said detection
result of said directly connectable node, wherein said third step
is a step for preferentially selecting the relay node installation
point candidate directly connectable to the isolated node said
duplication quantity of which is low and yet directly connectable
to other isolated node.
5. The method according to claim 2, said method further comprising
a fifth step for calculating the duplication quantity indicating
the number of relay node installation point candidates to which the
isolated node is directly connectable based on said detection
result of said directly connectable node, wherein said third step
is a step for preferentially selecting the relay node installation
point candidate directly connectable to the isolated node, said
duplication quantity of which is low, and yet directly connectable
to other isolated node.
6. The method according to claim 1, said method further comprising:
a sixth step for, when there are plural sets of relay node
installation points obtained in said third step, calculating the
duplication quantity indicating the number of relay node
installation points, to which the isolated node that has become
connectable to said base station is directly connectable, for each
set of relay node installation points based on said detection
result of said directly connectable node; and a seventh step for
selecting one set from among the plural sets of relay node
installation points based on said duplication quantity.
7. The method according to claim 2, said method further comprising:
a sixth step for, when there are plural sets of relay node
installation points obtained in said fourth step, calculating the
duplication quantity indicating the number of relay node
installation points, to which the isolated node that has become
connectable to said base station is directly connectable, for each
set of relay node installation points based on said detection
result of said directly connectable node; and a seventh step for
selecting one set from among the plural sets of relay node
installation points based on said duplication quantity.
8. The method according to claim 1, said method further comprising:
an eighth step for, when there are plural sets of relay node
installation points obtained in said third step, calculating an
average number of hops, which is an average of the number of hops
between a relay node installation point and said base station for
each set of relay node installation points; and a ninth step for
selecting one set from among the plural sets of relay node
installation points based on said average number of hops.
9. The method according to claim 2, said method further comprising:
an eighth step for, when there are plural sets of relay node
installation points obtained in said fourth step, calculating an
average number of hops, which is an average of the number of hops
between a relay node installation point and said base station for
each set of relay node installation points; and a ninth step for
selecting one set from among the plural sets of relay node
installation points based on said average number of hops.
10. A relay node installation point selection device for selecting
a relay node installation point used for forming a route between a
base station and an isolated node in a wireless multi-hop network
from among predetermined relay node installation point candidates,
said device comprising: an input section which receives a
node-to-node connectability diagnosis result by said base station
and a detection result of a directly connectable node for each of
said relay node installation point candidates; and a selection
processing section which selects, when it has been judged from said
node-to-node connectability diagnosis result that there exists the
isolated node, the relay node installation point candidate
connectable to said base station and yet directly connectable to
the isolated node as a relay node installation point based on said
detection result of said direct connectable node as a first
process.
11. The device according to claim 10, wherein said selection
processing section selects, when it has been judged as a result of
said first process that there still remains the isolated node
unconnectable to said base station, the relay node installation
point candidate directly connectable to the remaining isolated node
and yet directly connectable to the isolated node that has become
connectable to said base station from among relay node installation
point candidates non-connectable to said base station as a relay
node installation point based on said detection result of said
directly connectable node, as a second process.
12. The device according to claim 11, wherein said selection
processing sction further repeats said second process when it has
been judged that there still remains the isolated node
unconnectable to said base station even after said second
process.
13. The device according to claim 10, said device further
comprising a duplication quantity calculation section which
calculates a duplication quantity indicating the number of relay
node installation point candidates to which the isolated node is
directly connectable based on said detection result of said
directly connectable node, wherein said selection processing
section preferentially selects the relay node installation point
candidate directly connectable to the isolated node, said
duplication quantity of which is low, and yet directly connectable
to other isolated node that has not become yet connectable to said
base station as a relay node installation point.
14. The device according to claim 11, said device further
comprising a duplication quantity calculation section which
calculates duplication quantity indicating the number of relay node
installation point candidates to which the isolated node is
directly connectable based on said detection result of said
directly connectable node, wherein said selection processing
section preferentially selects the relay node installation point
candidate directly connectable to the isolated node, said
duplication quantity of which is low, and yet directly connectable
to other isolated node that has not become yet connectable to said
base station as a relay node installation point.
15. The device according to claim 10, said device further
comprising a duplication calculation section which calculates
duplication quantity indicating the number of relay node
installation points, to which the isolated node that has already
become connectable to said base station is directly connectable,
for each set of relay node installation points based on said
detection result of said direct connectable node, wherein said
selection processing section selects, when there are plural sets of
relay node installation points obtained in said first process, one
set from said plural sets of relay node installation points based
on said duplication quantity.
16. The device according to claim 11, said device further
comprising a duplication calculation section which calculates a
duplication quantity indicating the number of relay node
installation points, to which the isolated node that has already
become connectable to said base station is directly connectable,
for each set of relay node installation points based on said
detection result of said direct connectable node, wherein said
selection processing section selects, when there are plural sets of
relay node installation points obtained in said second process, one
set from said plural sets of relay node installation points based
on said duplication quantity.
17. The device according to claim 10, said device further
comprising an average hop-number calculation section which
calculates, for each of plural sets of relay node installation
points, an average number of hops, which is an average of the
number of hops between each relay node installation point included
therein and said base station, wherein said selection processing
section selects, when there are plural sets of relay node
installation points obtained in said first process by said
selection processing section, one set from said plural sets of
relay node installation points based on said average number of
hops.
18. The device according to claim 11, said device further
comprising an average number of hops calculation section which
calculates, for each of plural sets of relay node installation
points, an average number of hops being an average of the number of
hops between each relay node installation point included therein
and said base station, wherein said selection processing section
selects, when there are plural sets of relay node installation
points obtained in said second process by said selection processing
section, one set from a said plural sets of relay node installation
points based on said average number of hops.
19. A base station in a wireless multi-hop network having said base
station and plural nodes in which one part of said plural nodes is
connected to the base station via other nodes, said base station
comprising: a node-to-node connectability diagnosis section for
diagnosing direct connectability between said plural nodes and
direct connectability between each of said nodes and the base
station and outputts a node-to-node connectability diagnosis
result; an input section which receives, as detection result of
said direct connectable node, a detection result of the node to
which a direct connection is enabled by the relay node installation
point candidate; and a selection processing section which selects,
when it has been judged as said node-to-node connectability
diagnosis result that there exists the isolated node, the relay
node installation point candidate connectable to said base station
and yet directly connectable to the isolated node as a relay node
installation point based on said detection result of said direct
connectable node as a first process.
20. The base station according to claim 19, wherein said selection
processing section selects, when it has been judged as a result of
said first process that there still remains the isolated node
unconnectable to said base station, the relay node installation
point candidate directly connectable to the remaining isolated node
and yet directly connectable to the isolated node that has become
connectable to said base station from relay node installation point
candidates unconnectable to said base station as a relay node
installation point based on said detection result of said direct
connectable node as a second process.
21. A recording medium which records a program product which
causing a computer to execute a procedure for selecting a relay
node installation point used for forming a route between a base
station and an isolated node in a wireless multi-hop network from
predetermined relay node installation point candidates, said
program comprising the steps of: a first step for receiving a
node-to-node connectability diagnosis result by said base station;
a second step for, for each of said relay node installation point
candidates, receiving a detection result of the node to which a
direct connection is enabled by each relay node installation point
candidate; and a third step for, when it has been judged from said
node-to-node connectability diagnosis result that there exists the
isolated node, selecting the relay node installation point
candidate connectable to said base station and yet directly
connectable to the isolated node as an installation point of said
relay node based on said detection result.
22. The recording medium according to claim 21, said program
further comprising a fourth step for, when there still remains the
isolated node unconnectable to said base station after said third
step ends, selecting the relay node installation point directly
connectable to both the remaining isolated node and the isolated
node that has become connectable to said base station as a result
of said third step from relay node installation point candidates
that do not enable a connection to said base station as a relay
node installation point based on said detection result.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the invention
[0002] The present invention relates to a wireless multi-hop
network composed of nodes (wireless devices) having a wireless
multi-hop function.
[0003] 2. Description of the Related Art
[0004] A wireless sensor network is a network composed of wireless
sensor nodes having a sensor, and a base station. In this network,
the wireless node collects environmental information (temperature,
humidity, material content in the atmosphere, etc.) and transmits
the collection result to the base station.
[0005] In the wireless sensor network, the wireless multi-hop
network technique is used in many cases. The wireless multi-hop
network allows the transmission powers of the base station and each
node to be reduced and realizes reduction in power consumption by
carrying out packet transfer between the base station and the node
via one or plural other nodes. This technique is described in, for
example, the paper titled "Power-efficient multi-hop routing with a
message driven standby control" by Ohkuma et al. in the technical
Report of IEICE, NS003-232 (2003-01) (hereinafter, referred to as
"Document 1").
[0006] In the wireless multi-hop network, all of the nodes having a
wireless sensor must be communicatable with the base station.
Therefore, in the wireless multi-hop network, a relay node having a
reactive (passive) type routing function is installed at a
specified installation point.
[0007] In order to form the wireless multi-hop network, the base
station makes a node-to-node connectability diagnosis. The
node-to-node connectability diagnosis is made as follows. First,
the base station transmits a control signal to each node. Then, the
node that has received the control signal returns a response to the
control signal to the base station. In this manner, the base
station grasps the connection relationships between the base
station and the node and between nodes based on the response from
each node.
[0008] However, as shown in FIG. 1, there may appear a group of
nodes connectable to the base station (hereinafter, referred to as
a "base station group") and a group of isolated nodes unconnectable
to the base station (hereinafter, referred to as an "isolated node
group"). As a matter of course, the isolated node is not
communicatable with the base station. Therefore, the relay node is
installed in order to connect the isolated node to the base
station.
[0009] Conventionally, the relay nodes are installed on a basis of
trial and error. In other words, first, the relay node is
temporarily installed at an appropriate installation point and then
the base station makes a node-to-node connectability diagnosis. In
this manner, the base station confirms whether or not the isolated
node is eliminated.
[0010] However, in the conventional method, the isolated node is
far from being eliminated in many cases. Therefore, a network
designer used to change the relay node installation point many
times and repeat the same procedure. Therefore, the determination
of the relay node installation point requires many man-hours.
SUMMARY OF THE INVENTION
[0011] An exemplary feature of the present invention provides a
technique for reducing man-hours required for installing a relay
node in a wireless multi-hop network.
[0012] One aspect of the present invention carries out a first
process and a second process described below.
[0013] In the first process, a selection processing section
acquires a node-to-node connectability diagnosis result by a base
station and a detection result of a node connectable in one hop
(that is, "directly connectable") at a relay node installation
point candidate.
[0014] Here, the latter result can be obtained by temporarily
installing a wireless device having a function of detecting a
directly connectable node at each relay node installation point
candidate and operating it.
[0015] When it is judged from the node-to-node connectability
diagnosis result that the isolated node is present, the selection
processing section performs the first process. In the first
process, the selection processing section selects the relay node
installation point candidate that satisfies the following two
conditions:
[0016] (1) the relay node installation point candidate enabling a
connection to the base station (that is, the relay node
installation point candidate enabling a one-hop connection to the
base station or the nodes belonging to the base station group);
and
[0017] (2) the relay node installation point candidate enabling a
one-hop connection to the isolated node.
[0018] With the first process, a route of "isolated node>relay
node >base station" is established for one part of or all of the
isolated nodes.
[0019] At the time point that the first process has been completed,
if there still remains the isolated node, the selection processing
section carries out the second process. In the second process, the
selection processing section selects the relay node installation
point candidate that satisfies the following condition from among
relay node installation point candidates that do not enable a
connection to the base station:
[0020] the relay node installation point candidate enabling a
direct connection (that is, enabling a connection to be made in one
hop) to both the remaining isolated node and the node that has
become connectable to the base station in the first process.
[0021] With the second process, a route of "remaining isolated
node>relay node>isolated node that has become connectable to
the base station in the first process>relay node>base
station" is established.
[0022] According to the aspect of the present invention, using the
node-to-node connectability diagnosis result by the base station
and the detection result of the node connectable in one hop at the
relay node installation point candidate, thereby to select the
relay node installation point candidate for establishing a
connection between the base station and the isolated node makes it
possible to reduce the number of changes of the relay node
installation point candidate.
[0023] The description of preferred embodiments will clear other
features and aspects of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In the accompanying drawings:
[0025] FIG. 1 is a diagram for explaining a wireless multi-hop
network;
[0026] FIG. 2 is a block diagram for explaining a relay node
installation point selection device of the present invention;
[0027] FIG. 3 is a flow chart for explaining a relay node
installation point selection procedure in embodiment 1 of the
present invention; and
[0028] FIG. 4A and FIG. 4B are flow charts for explaining a relay
node installation point selection procedure in embodiment 2 of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] The following is the detailed explanation of embodiments of
the present invention with reference to drawings.
[0030] FIG. 1 is a diagram showing a wireless multi-hop
network.
[0031] In FIG. 1, nodes 1 to 4 are nodes connectable to a base
station 50, forming a base station group. Nodes 5 to 11 are
isolated nodes unconnectable to the base station 50, forming an
isolated node group. Reference symbols A to J denote relay node
installation point candidates. In the network shown in FIG. 1, the
relay node installation point is selected from among these relay
node installation point candidates A to J.
[0032] FIG. 2 is a block diagram for explaining the configuration
of a relay node installation point selection device according to
the present invention.
[0033] A relay node installation point selection device 2 includes
an input section 21, a selection processing section 22, a storage
section 23, a duplication quantity calculation section 24, and an
average hop-number calculation section 26. However, the duplication
quantity calculation section 24 and the average hop-number
calculation section 26 are optional as will be described later. For
example, the embodiment 1 does not require these two calculation
devices.
[0034] The input section 21 receives a node-to-node connectability
diagnosis result by the base station, a detection result of the
node connectable in one hop at a relay node installation point
candidate, etc., as an input. The former input is supplied from,
for example, the base station.
[0035] The selection processing section 22 records data, which the
input section 21 has received, in the storage section 23 in table
form, for example. Then, based on the data stored in the storage
section 23 and data obtained by processing the above data by the
selection processing section 22 itself, the selection processing
section 22 selects the relay node installation point from among
relay node installation point candidates.
[0036] As will be described later, in embodiment 2 and embodiment
3, based on the data that the selection processing section 22
itself and the duplication quantity calculation section 24 have
recorded, the selection processing section 22 selects the relay
node installation point from among relay node installation point
candidates. In embodiment 4, based on the data that the selection
processing section 22 itself and the average hop-number calculation
section 26 have recorded, the selection processing section 22
selects the relay node installation point from among relay node
installation point candidates.
[0037] The storage section 23 stores the data that the input
section 21 has received, data obtained by processing the above data
by the selection processing section 22, data that the duplication
quantity calculation section 24 and the average hop-number
calculation section 26 have recorded, etc. in the table form, for
example.
[0038] The calculation section 24 is necessitated in a relay node
installation point selection method in the embodiment 2 and the
embodiment 3, which will be described later. Here, the duplication
quantity means the number of relay node installation point
candidates enabling a connection to the isolated node to be made in
one hop. Based on the data stored in the storage section 23 which
the input section 21 has received, and data obtained by processing
the above data by the selection processing section 22, the
duplication quantity calculation section 24 calculates the
duplication quantity and records it in the storage section 23. In
the embodiment 3, the duplication quantity calculation section 24
calculates the duplication quantity for each of plural sets of
relay node installation point candidates.
[0039] The average hop-number calculation section 26 is
necessitated in a relay node installation point selection method in
embodiment 4, which will be described later. The so-called average
number of hops is the average of the number of hops between each
node and the base station in a set of relay node installation point
candidates selected by the selection processing section 22.
[0040] Here, the so-called number of hops is equal to the number
obtained by adding one (1) to the number of other nodes existing on
a route connecting a certain node and the base station. For
example, in FIG. 1, the numbers of hops of the nodes 1, 2, 3, and 4
are 1, 2, 2, and 3, respectively. The average hop-number
calculation section 26 calculates the average number of hops based
on the data stored in the storage section 23 which the input
section 21 has received and data obtained by processing the above
data by the selection processing section 22, etc. The average hop
number calculation section files the calculated value in the
storage section 23.
Embodiment 1
[0041] Referring to FIG. 3, shown is a flow chart for explaining
the procedure of the relay node installation point selection method
in the embodiment 1 of the present invention.
[0042] In step 301, the input section 21 receives a node-to-node
connectability diagnosis result by the base station and a detection
result of the nodes to which a connection is enabled in one hop by
the relay node installation point candidate. The selection
processing section 22 records them in the storage section 23.
[0043] Table 1 is a list that the selection processing section 22
has prepared based on the node-to-node connectability diagnosis
result by the base station and has filed in the storage section 23.
This list describes the number of hops for node IDs.
[0044] Here, the so-called number of hops is equal to the number
obtained by adding one (1) to the number of the nodes existing on a
route connecting the base station and a certain node. For example,
in FIG. 1, the numbers of hops of the node 1 to node 4 are 1, 2, 2,
and 3, respectively. With other nodes 5 to 11, the connection to
the base station has not been established yet, so the numbers of
hops thereof are zero. TABLE-US-00001 TABLE 1 node ID number of
hops 1 1 2 2 3 2 4 3 5 0 6 0 7 0 8 0 9 0 10 0 11 0
[0045] Table 2 is a list that the selection processing section 22
has prepared based on the detection result of the nodes connectable
to the relay node installation point candidate in one hop and Table
1, and has stored in the storage section 23. The list records IDs
of the nodes (nodes belonging to the isolated node group) to which
a connection is enabled in one hop by the relay node installation
point candidate. In each row of isolated nodes 5 to 11, "1"
indicates that a connection is enabled in one hop and "0" indicates
that a connection is not enabled in one hop. Further, this list
describes node IDs of the nodes belonging to the base station group
connectable in one hop for each of relay node installation points A
to J. The relay node installation point candidates that do not
enable a connection to the nodes belonging to the base station
group to be made in one hop are described as "none".
[0046] For example, the column of the relay node installation point
candidate B in Table 2 indicates that relay node installation point
candidate B enables a connection to the isolated node 8 to be made
in one hop and enables a connection to the node 4 belonging to the
base station group to be made in one hop. Further, the column of
the relay node installation point candidate A in Table 2 indicates
that the relay node installation point candidate A enables a
connection to the isolated node 8 to be made in one hop and does
not enable a connection to any node belonging to the base station
group to be made in one hop. TABLE-US-00002 TABLE 2 RESULT LIST A B
C D E F G H I J isollated 5 0 0 1 1 0 0 0 0 1 0 node ID 6 0 0 0 1 1
0 1 0 1 0 7 0 0 0 0 0 0 1 0 0 0 8 1 1 0 0 0 0 0 0 0 1 9 0 0 1 1 0 0
0 0 1 0 10 0 0 0 1 1 0 1 0 1 0 11 0 0 0 0 0 1 0 1 0 0 node ID of
base none 4 2 3 3 3 none none none none station group
[0047] In step 301, the selection processing section 22 first
judges whether or not the isolated node exists based on Table 1
(the node-to-node connectability diagnosis result by the base
station). In the example of Table 1, since the numbers of hops of
the nodes 5 to 11 are zero, the selection processing section 22
judges that there exists the isolated node. At this time, if there
is no isolated node, it becomes clear that the installation of the
relay node installation point is not necessary.
[0048] When it has been judged that there exists the isolated node,
the selection processing section 22 selects the relay node
installation point candidate that satisfies the following
conditions based on Table 2 (the detection result of the nodes
connectable in one hop at the relay node installation point), in
other words:
[0049] (1) the relay node installation point candidate enabling a
connection to the isolated node to be made in one hope; and yet
[0050] (2) the relay node installation point candidate enabling a
connectable to the base station, that is, the relay node
installation point candidate enabling a connection to the node
belonging to the base station group to be made in one hop.
[0051] With the above-mentioned process, a route is established of
"isolated node>relay node>base station".
[0052] In the example in FIG. 1, the selection processing section
22 selects, for example, candidate C (for isolated nodes 5 and 9),
candidate D (for isolated nodes 6 and 10), candidate B (for
isolated node 8), and candidate F (for isolated node 11) from among
the relay node installation point candidates A to J.
[0053] In this selection, the selection processing section 22
selects the relay node installation point candidate located at the
leftmost side in each row from among the relay node installation
point candidates that satisfy the above-mentioned conditions
(however, it does not select the same candidates repeatedly). Other
selection criteria will be apparent to those skilled in the art.
For example, it may be possible to select all relay node
installation point candidates B, C, D, E, and F connectable to the
base station.
[0054] As a result, the connection between each of the isolated
nodes 5, 6, 8, 9, 10, and 11 and the base station is
established.
[0055] At this time, a new row is provided in Table 2, and in the
new row, the box of the isolated node that has become connectable
to the base station by the selection of this one set of relay node
installation point candidates is marked. Further, another new row
is provided in Table 2, and in this new row, the box of the
selected relay node installation point candidate is marked. It may
be possible to carry out this process by separately preparing
tables for recording the selected relay node installation point
candidate and the ID of the node that has become connectable owing
to this selection and filing them in the storage section 23.
[0056] Here, for details of the node-to-node connectability
diagnosis by the base station, refer to, for example, Document 1
described above.
[0057] The routing described in Document 1 is as follows.
[0058] That is, the base station sequentially transmits a detection
signal to each node. Only the nodes that have received the
detection signal at intensity stronger than predetermined intensity
directly return a detection response signal to the base station.
Due to this, a connectability between the base station and the node
that has returned the detection response signal is established.
Next, the base station sequentially transmits the detection signal
to each node to which a connection has not been established yet via
the node to which a connection has been already established. Only
the nodes that have received the detection signal at intensity
stronger than predetermined intensity return the detection response
signal to the base station via the relay node. Due to this, the
node that was directly unconnectable to the base station is
connected to the base station via the node that was directly
connectable to the base station. By repeating the above-mentioned
process, the wireless multi-hop network is formed, and together
therewith, the connection relationship between the base station and
each node becomes clear.
[0059] The detection of the node connectable in one hop at the
relay node installation point candidate is carried out, for
example, as follows. First, a wireless device (may be one for the
base station) having a function of detecting the node connectable
in one hop is installed at each relay node installation point
candidate. Then, when the device is caused to operate, it tries to
communicate with all the nodes, thereby making it possible to find
the nodes communicatable in one hop at the relay node installation
point candidate. It is possible to obtain the detection result also
by limiting the AODV routing technique regulated by IETF RFC3561 or
the like to the process up to one hop to use it.
[0060] The explanation of the step 301 ends as above.
[0061] In step 302, the selection processing section 22 judges
whether or not there still remains the isolated node in an
"unconnected state" with the base station based on the execution
result of the step 301. Here the so-called "unconnected state"
means that any connection to the base station has not been
established yet. In the example shown in Table 2, since the node 7
is in the "unconnected state" with the base station, the process of
the selection processing section 22 proceeds to step 303. If there
remains no isolated node in the "unconnected state" as a result of
the process in the step 301, the process of the selection
processing section 22 ends.
[0062] In the step 303, the selection processing section 22 selects
the relay node installation point candidate that satisfies the
following conditions from among relay node installation point
candidates in which a connection to the node belonging to the base
station group has not been made based on Table 2 (the detection
result of the node connectable in one hop at the relay node
installation point candidate):
[0063] (1) the relay node installation point candidate enabling a
one-hop connection to the node that has become connectable to the
base station (in the process in the step 301); and yet
[0064] (2) the relay node installation point candidate enabling a
one-hop connection to the isolated node to be made in one hop.
[0065] Speaking the example in Table 2, the isolated node 7 that
has been left is connectable in one hop to the relay node
installation point G, though unconnectable in one hop to the node
in the base station group. However, the relay node installation
point G enables a connection to the node 10 of which a connection
to the base station has been established in the step 301.
Therefore, since the relay node installation point candidate
satisfies these conditions, the relay node installation point G is
selected in the step 303. Due to this, the node 7 that has been
left as an isolated node in the process in the step 301 also now
becomes connectable to the base station. In other words, a
connection through "node 7>relay node G>node 6>relay node
D> . . . >base station" is established.
[0066] In step 304, the selection processing section 22 judges
whether or not there still remains the isolated node in the
"unconnected state" based on the detection result of the node
connectable in one hop at the relay node installation point
candidate. If there remains the isolated node in the "unconnected
state", the process of the selection processing section 22 proceeds
to step 305, and otherwise, the process of the selection processing
section 22 ends.
[0067] In the step 305, the selection processing section 22 repeats
the process in the step 303, or returns to the step 303 and starts
from scratch by reselecting the relay node installation point
candidate again. When the number of repetitions reaches a
predetermined number, it may be possible to select the relay node
installation point candidate again in the step 303.
[0068] In the embodiment 1 described above, the step 303 is
executed only when there remains the isolated node at the time when
the process in step 302 ends. Therefore, when it is possible to
prepare a sufficient number of the relay node installation point
candidates, all the nodes belonging to the isolated node group are
made connectable to the base station without carrying out the
processes in the step 303 and the subsequent steps. Further, even
if the process has ended in the step 303, many isolated nodes have
become connectable to the base station, so man-hours also required
for changing the relay node installation point candidate can be
small. Therefore, in such a case, the processes in the step 302 and
the subsequent steps are not necessarily indispensable.
Embodiment 2
[0069] FIG. 4A and FIG. 4B are flow charts showing a relay node
installation point selection procedure in the embodiment 2
according to the present invention.
[0070] This embodiment is for the relay node installation point
selection procedure that minimizes the number of the relay nodes.
Due to this embodiment, it is possible to reduce the number of the
nodes in the wireless multi-hop network and to effectively utilize
the resource as well as to make a contribution to the power saving
of the entire network.
[0071] In this embodiment, the duplication quantity calculation
section 24 calculates the duplication quantity (that is, the number
of the relay node installation point candidates to which each
isolated node is connectable in one hop). Then, the selection
processing section selects the relay node installation point
candidate while taking the duplication quantity into account. Due
to this, this embodiment requires the duplication quantity
calculation section 24. The duplication quantity calculation
section 24 calculates the duplication quantity based on the data
stored in the storage section 23, which the input section 21 has
received, data obtained by processing the above data by the
selection processing section 22, etc., and records it in the
storage section 23
[0072] In step 401, similarly to the embodiment 1, the input
section 21 receives the "node-to-node connectability diagnosis
result by the base station". Then, the selection processing section
22 prepares a table showing the relationship between the node and
the number of hops based on this. In the example in FIG. 1, the
selection processing section 22 prepares Table 1 and records it in
the storage section 23. As for Table 1, explanation is the same as
that in the embodiment 1.
[0073] In step 402, the selection processing section 22 judges
whether or not there exists the isolated node based on Table 1 (the
table showing a correspondence between the node and the number of
hops). In Table 1, if there exists the node the hop number of which
is zero, the selection processing section 22 judges that there
exists the isolated node. In Table 1, the numbers of hops of the
node 5 to node 11 are zero, the selection processing section 22
judges that there exists the isolated node. When the selection
processing section 22 judges that there exists the isolated node,
the process of the selection processing section 22 proceeds to step
403 and otherwise, the selection processing section 22 ends the
process.
[0074] In the step 403, the input section 21 receives the detection
result of the node connectable in one hop at each relay node
installation point candidate. The selection processing section 22
prepares a table showing a one-hop-connection relationship between
the isolated node and the relay node installation point candidate
and files it in the storage section 23. Table 2 described above is
a table prepared for the network in FIG. 1.
[0075] Table 2 is a table showing the one-hop-connection
relationship between the isolated node and the relay node
installation point candidate in the wireless multi-hop network in
FIG. 1. As for Table 2 also, explanation is the same as that in the
embodiment 1, so the duplicated explanation is omitted here.
[0076] Further, the selection processing section 22 classifies
Table 2 into two tables. One is a table for the relay node
installation point candidates in which a connection to the base
station has been made. The other is a table for the relay node
installation point candidates in which a connection to the base
station has not been made. The selection processing section 22
files the former as result list A (Table 3) and the latter as
result list A' (Table 4) in the storage section 23.
[0077] Table 3 and Table 4 are the result list A, and the result
list A' classified from Table 2, respectively. As described above,
the box of the "node ID of the base station group" indicates the ID
of the node belonging to the base station group to which a
connection is enabled in one hop by the relay node installation
point candidate. Therefore, the relay node installation point
candidate having the number described in the box of the "node ID of
the base station group" enables a connection to the base station.
The relay node installation point candidate having "none" described
in the box of the "node ID of the base station group" does not
enable a connection to the base station.
[0078] In step 404, Table 2 is classified into Table 3 and Table 4
based on the node ID of the base station group. With table 2, the
columns of the relay node installation point candidates B, C, D, E,
and F are classified into Table 3. The columns of the relay node
installation point candidates A, G, H, I, and J in Table 2 are
classified into Table 4. TABLE-US-00003 TABLE 3 RESULT LIST A B C D
E F isollated 5 0 1 1 0 0 node ID 6 0 0 1 1 0 7 0 0 0 0 0 8 1 0 0 0
0 9 0 1 1 0 0 10 0 0 1 1 0 11 0 0 0 0 1 node ID of base 4 2 3 3 3
station group
[0079] TABLE-US-00004 TABLE 4 RESULT LIST A' A G H I J isolated 5 0
0 0 1 0 node ID 6 0 1 0 1 0 7 0 1 0 0 0 8 1 0 0 0 1 9 0 0 0 1 0 10
0 1 0 1 0 11 0 0 1 0 0 node ID of base none none none none none
station group
[0080] In this embodiment, the following processes (1) and (2) are
carried out in order. The classification into the result list A,
and the result list A' is carried out for convenience of carrying
out the two processes.
[0081] (1) A process for establishing a route of: isolated
node>relay node>base station
[0082] (2) A process for establishing a route of: isolated node in
an "unconnected state">relay node>isolated node in an
"already connected state">base station
[0083] Here, the "unconnected state" means a state in which any
connection with the base station has not been established even with
the process (1). The "already connected state" means a state in
which a connection with the base station has been established by
installing the relay node.
[0084] Subsequent step 404 to step 409 correspond to the process
(1) and step 410 to step 416 correspond to the process (2).
[0085] In the step 404, the duplication quantity calculation
section 24 calculates the duplication quantity of each isolated
node based on the result list A (Table 3) stored in storage section
23. Then, the duplication quantity calculation section 24 prepares
Table 5, which is the result list A to which the duplication
quantity is written additionally, and files it in the storage
section 23. The duplication quantity can be obtained by summing up
the values in the row. TABLE-US-00005 TABLE 5 RESULT LIST A
duplication B C D E F quantity isolated 5 0 1 1 0 0 2 node ID 6 0 0
1 1 0 2 7 0 0 0 0 0 0 8 1 0 0 0 0 1 9 0 1 1 0 0 2 10 0 0 1 1 0 2 11
0 0 0 0 1 1 node ID of base 4 2 3 3 3 station group
[0086] Next, in the step 405, the selection processing section 22
selects the relay node installation point candidate enabling a
one-hop connection to the isolated node with duplication quantity 1
in the result list A (Table 5) including the duplication quantity
stored in the storage section 23.
[0087] In Table 5, the isolated nodes with duplication quantity 1
are the node 8 and the node 11. Then, the relay node installation
point candidates enabling one-hop connections to the node 8 and the
node 11 are B and F, respectively. Therefore, the selection
processing section 22 selects B and F as a relay node installation
point. Then, by selecting B and F as a relay node installation
point, the following two connection routes are established:
[0088] isolated node 8>relay node B>(node 4>node 2>node
1)>base station 50; and
[0089] isolated node 11>relay node F>(node 3>node
1)>base station 50.
[0090] At this time, if there exists another isolated node
connectable to the relay node B and the relay node F in one hop, a
connection route with the base station is established for this
isolated node as well simultaneously. In Table 5, there happens to
exist no such isolated node. Therefore, in this stage, a connection
route with the base station is established for the isolated node 8
and the isolated node 11.
[0091] In this embodiment, the reason for establishing a route
starting from the isolated node with duplication quantity 1 is to
reduce the number of the relay nodes. By using the relay node
selected through a route established with the isolated node with a
low duplication quantity also in a route with the isolated node
with a high duplication quantity, it is possible to reduce the
number of the relay nodes.
[0092] In the step 406, the selection processing section 22 judges
whether or not there exists the isolated node in the "unconnected
state" with duplication quantity 2 or higher based on the result
list A (Table 5) including the duplication quantity. In table 5,
since the node 5, the node 6, the node 9, and the node 10 are the
isolated nodes with duplication quantity 2 in the "unconnected
state", the selection processing section 22 judges that there
exists the isolated node in the "unconnected state" with
duplication quantity 2 or higher. When it has been judged that
there exists the isolated node in the "unconnected state" with
duplication quantity 2 or higher, the process of the selection
processing section 22 proceeds to the step 407. When it has been
judged that there exist no isolated node with duplication quantity
2 or higher in the "unconnected state", the selection processing
section 22 proceeds to the step 409 of judging whether or not to
start the establishment of a route of isolated node "in an
unconnected state">relay node>isolated node "in an already
connected state">base station.
[0093] In the step 407, the selection processing section 22 selects
the relay node installation point candidate that satisfies the
following conditions:
[0094] (a) the relay node installation point candidate enabling a
connection to the isolated node with the minimum duplication
quantity (2 or higher) in the "unconnected state" to be made in one
hop; and yet
[0095] (b) the relay node installation point candidate enabling a
one-hop connection to the isolated nodes in the "unconnected state"
more numerously.
[0096] In Table 5, the isolated nodes with minimum duplication
quantity 2 in the "unconnected state" are the node 5, the node 6,
the node 9, and the node 10.
[0097] Then, the relay node installation point candidates enabling
a one-hop connection to the node 5 are C and D. C enables a one-hop
connection to the node 9, which is the isolated node in the
"unconnected state". On the other hand, D enables a one-hop
connection to the node 6, the node 9, and the node 10, which are
the isolated nodes in the "unconnected state". Therefore, D
enabling a one-hop connection to the isolated nodes in the
"unconnected state" more numerously is selected for the node 5.
Similarly, D is selected for the node 6, the node 9, and the node
10 as well. As a result, the following four connection routes are
newly established:
[0098] Isolated node 5>relay node D>(node 3>node
1)>base station 50
[0099] Isolated node 6>relay node D>(node 3>node
1)>base station 50
[0100] Isolated node 9>relay node D>(node 3>node
1)>base station 50
[0101] Isolated node 10>relay node D>(node 3>node
1)>base station 50
[0102] As described above, by preferentially selecting the relay
node installation point candidate enabling a connection to the
isolated nodes in the "unconnected state" to be made in one hop
more numerously, it is possible to reduce the number of relay
nodes.
[0103] Next, in the step 408, the selection processing section 22
judges whether or not there remains the isolated node with
duplication quantity 2 or higher in the "unconnected state" based
on Table 5, which is the result list A including the duplication
quantity. In the case of Table 5, since there remains no isolated
node with duplication quantity 3 or higher (the isolated node with
duplication quantity 2 in the "unconnected state" no longer
exists), the selection processing section 22 judges that there
exists no isolated node with duplication quantity 2 or higher in
the "unconnected state".
[0104] When the judgment result in the step 408 is "NO", the
process of the selection processing section 22 proceeds to the step
409. Otherwise, the process of the selection processing section 22
returns to the step 407.
[0105] In the step 409, the selection processing section 22 judges
whether or not there exists the isolated node with duplication
quantity 0 in the "unconnected state" based on Table 5, which is
the result list A including the duplication quantity. In Table 5,
the node 7 is an isolated node with duplication quantity 0 in the
"unconnected state", so the selection processing section 22 judges
that there exists the isolated node with duplication quantity 0 in
the "unconnected state". When the selection processing section 22
has judged that there exists the isolated node in the "unconnected
state" with duplication quantity 0 (YES), the process of the
selection processing section 22 proceeds to the step 410.
Otherwise, the selection processing section 22 ends the
process.
[0106] The isolated node in the "unconnected state" with
duplication quantity 0 is directly unconnectable to the relay node
installation point candidate at which a connection to the base
station has been made. As a result, it is not possible to make a
connection to the base station.
[0107] In this embodiment, it is detected whether or not the relay
node installation point candidate (X) to which the isolated node
(x) in the "unconnected state" is connectable in one hop enables a
connection to the isolated node (y) that has already become
connectable to the base station. If a connection between X and y is
enabled, the selection processing section 22 establishes a
connection between the isolated node (x) in the "unconnected state"
and the base station using a route via the "already connected"
isolated node.
[0108] In other words, the selection processing section 22
establishes a connection as follows:
[0109] isolated node (x) in an "unconnected state"
[0110] relay node (relay node installed at the relay node
installation point (X) in which a connection to the base station
has not been made)
[0111] isolated node (y) in an "already connected state"
[0112] base station.
[0113] The establishment of the connection is carried out, by
selecting the relay node installation point candidate (X) in which
a connection to the base station has not been made as a relay node
installation point.
[0114] Returning to FIG. 4B, in the step 410, the selection
processing section 22 classifies the result list A' (Table 4: a
table showing a one-hop-connection relationship between the
isolated node and the relay node installation point candidate in
which a connection to the base station has not been made) into two
parts. One part relates to the relay node installation point
candidates enabling a one-hop connection to the isolated node in
the "already connected state". The other part relates to relay node
installation point candidates that does not enables a one-hop
connection to the isolated node in the "already connected state".
The selection processing section 22 files the former as the result
list B' (Table 6) in the storage section 23.
[0115] In Table 4, the isolated nodes in the "already connected
state" are the node 5, the node 6, the node 8, the node 9, the node
10, and the node 11. Therefore, the selection processing section 22
extracts the columns of A (node 8), G (node 6, node 10), H (node 11
), I (node 5, node 6, node 9, node 10), and J (node 8) as a relay
node installation point candidate enabling a connection to the
isolated node in the "already connected state" to be made in one
hop and prepares Table 6. TABLE-US-00006 TABLE 6 RESULT LIST B'
duplication A G H I J quantity isolated 5 0 0 0 1 0 1 node ID 6 0 1
0 1 0 2 7 0 1 0 0 0 1 8 1 0 0 0 1 2 9 0 0 0 1 0 1 10 0 1 0 1 0 2 11
0 0 1 0 0 1 node ID of base none none none none none station
group
[0116] In the step 411, the duplication quantity calculation
section 24 calculates the duplication quantity of each isolated
node based on Table 6, which is the result list B'. In Table 6, the
calculation results of the duplication quantity also have been
already described.
[0117] In the step 412, the selection processing section 22 selects
the relay node installation point candidate enabling a one-hop
connection to the isolated node with duplication quantity 1 in the
"unconnected state" based on the result list B' (Table 6). In Table
6, the isolated node with duplication quantity 1 in the
"unconnected state " is the node 7 only. Further, the relay node
installation point candidate enabling a one-hop connection to the
node 7 is only G. Therefore, the selection processing section 22
selects the relay node installation point candidate G.
[0118] As a result, the following route is newly established:
[0119] isolated node 7>relay node G>isolated node 6 in an
"already connected state">(relay node D>node 3>node
1)>base station 50; or
[0120] isolated node 7>relay node G>isolated node 10 in an
"already connected state">(relay node D>node 3>node
1)>base station 50.
[0121] In the step 413, the selection processing section 22 judges
whether or not there exists the isolated node with duplication
quantity 2 or higher in the "unconnected state" based on the result
list B' (Table 6). In Table 6, there exists no isolated node with
duplication quantity 2 or higher in the "unconnected state" (all of
the isolated nodes are in the "already connected state"). When the
selection processing section 22 has judged that there exists no
isolated node with duplication quantity 2 or higher in the
"unconnected state" (branching to NO in the step 413), the process
of the selection processing section 22 proceeds to the step 416.
Otherwise (branching to YES in the step 413), the process of the
selection processing section 22 proceeds to the step 414.
[0122] In the step 414, the selection processing section 22 selects
the relay node installation point candidate enabling a one-hop
connection to the "unconnected" isolated node with the minimum
duplication quantity (2 or higher) and yet the relay node
installation point candidate enabling a one-hop connection to the
"unconnected" isolated nodes more numerously based on the result
list B' (Table 6).
[0123] In the step 415, the selection processing section 22 judges
whether or not there exists the "unconnected" isolated node with
duplication quantity 2 or higher based on the result list B' `able
6). When the selection processing section 22 has judged that there
exists no "unconnected" isolated node with duplication quantity 2
or higher (branching to NO), the process of the selection
processing section 22 proceeds to the step 416. Otherwise, the
process of the selection processing section 22 returns to the step
414.
[0124] In the step 416, the selection processing section 22 judges
whether or not there exists the isolated node with duplication
quantity 0 in the "unconnected state" based on the result list B'
(Table 6). In Table 6, there is no isolated node with duplication
quantity 0 in the "unconnected state". When the selection
processing section 22 has judged that there exists no isolated node
with duplication quantity 0 in the "unconnected state" (NO), the
process of the selection processing section 22 ends. Otherwise, the
process of the selection processing section 22 proceeds to the step
417.
[0125] In the Step 417, the process similar to that of the steps
410 to 416 is repeated, or the relay node installation point
candidate is selected again to carry out the process from scratch.
If the repetition of the processes in the steps 410 to 416 for a
predetermined times does not eliminate the isolated node in the
"unconnected state", it may be possible to select the relay node
installation point candidate set again and to carry out the
processes in the steps 410 to 416.
[0126] Installation of the relay node at the relay node
installation point obtained as above causes the isolated node to be
connected to the base station. Table 7 is a table showing a
relationship between the node and the number of hops when selecting
the relay node installation point with the processes in the step
401 to step 417 and installing the relay node at the point for the
wireless multi-hop network shown in FIG. 1. TABLE-US-00007 TABLE 7
node ID number of hops 1 1 2 2 3 2 4 3 5 4 6 4 7 6 8 5 9 4 10 4 11
4 B 4 D 3 F 3 G 5
[0127] The established routes are summarized as follows.
[0128] node 1>base station 50
[0129] node 2>node 1>base station 50
[0130] node 3>node 1>base station 50
[0131] node 4>node 2>node 1>base station 50
[0132] node 5>relay node D>node 3>node 1>base station
50
[0133] node 6>relay node D>node 3>node 1>base station
50
[0134] node 7>relay node G>node 6>relay node D>node
3>node 1>base station 50 (or, node 7>relay node G>node
10>relay node D>node 3>node 1>base station 50)
[0135] node 8>relay node B>node 4>node 2>node 1>base
station 50
[0136] node 9>relay node D>node 3>node 1>base station
50
[0137] node 10>relay node D>node 3>node 1>base station
50
[0138] node 11>relay node F>node 3>node 1>base station
50
[0139] relay node B>node 4>node 2>node 1>base station
50
[0140] relay node D>node 3>node 1>base station 50
[0141] relay node F>node 3>node 1>base station 50
[0142] relay node G>node 10>relay node D>node 3>node
1>base station 50
Embodiment 3
[0143] The following is the explanation of a relay node
installation point selection method in embodiment 3 of the present
invention.
[0144] This embodiment is for a relay node installation point
selection method for selecting a set of relay node installation
point candidates for increasing the redundancy of the route.
According to this embodiment, even if, for example, communication
trouble occurs in one route, it becomes possible to switch the
route to another route.
[0145] In this embodiment, the selection processing section
calculates the duplication quantity using the duplication quantity
calculation section for each of plural sets of relay node
installation point candidates. Based on the result, the selection
processing section selects one relay node installation point
candidate set from among the plural sets. A concrete explanation is
as follows.
[0146] For example, let's assume that Table 8 and Table 9 are
obtained in the embodiment 1 or the embodiment 2, which are a
one-hop-connection relationship between the isolated node and the
relay node installation point candidate in plural sets of relay
node installation point candidates. By the way, Table 8 and Table 9
relate to a wireless multi-hop network different from that to which
Table 1 to Table 7 relate. TABLE-US-00008 TABLE 8 candidate set I
duplication A B C D quantity isolated 5 1 0 1 1 3 node ID 6 0 0 1 0
1 7 1 0 0 0 1 8 1 1 0 0 2 9 0 1 1 0 2 10 0 0 0 1 1 11 0 1 0 0 1
node ID of base none 4 2 3 station group
[0147] TABLE-US-00009 TABLE 9 candidate set II duplication B C D F
quantity isolated 5 0 1 1 1 3 node ID 6 0 1 0 0 1 7 0 0 0 1 1 8 1 0
0 1 2 9 1 1 0 0 2 10 0 0 1 1 2 11 1 0 0 0 1 node ID of base 4 2 3
None station group
[0148] The duplication quantity calculation section 24 calculates
the redundancy by calculating the sum of the elements in each row
of Table 8 and Table 9. Then, the selection processing section 22
selects the relay node installation point candidate set in which
the number of the isolated nodes with duplication quantity 2 or
higher becomes numerous. The number of isolated nodes with
duplication quantity higher than 2 in candidate set I is smaller
than that in the candidate set II. Therefore, the selection
processing section 22 selects the relay node installation point
candidate in Table 9. In this selection, it may be possible to take
into account the value itself of the duplication quantity. In other
words, it may be possible to calculate the average duplication
quantity of each set and to select the candidate set based on the
result.
Embodiment 4
[0149] The following is the explanation of a relay node
installation point selection method in embodiment 4 of the present
invention.
[0150] This embodiment is for a relay node installation point
selection method for selecting the relay node installation point
candidate set in which the number of hops of the isolated node is
lessened. According to this embodiment, since it is possible to
reduce the number of hops of the isolated node as small as
possible, the preferable effect in communication such as reduction
in transfer time is obtained.
[0151] In this embodiment, the average number of hops, i.e. the
average value of the number of hops of the relay node installation
point candidates and the base station in the relay node
installation point candidate set selected by the selection
processing section 22 is calculated by the average hop-number
calculation section 26 to select a proper relay node installation
point candidate set from among the plural relay node installation
point candidate sets based upon this. It is possible to reduce the
number of hops of the isolated node by reducing the number of hops
of the relay node installation point candidate. A concrete
explanation is as follows.
[0152] For example, let's assume that Table 8 and Table 9 showing a
one-hop-connection relationship between the isolated node and the
relay node installation point candidate in the two relay node
installation point candidate sets are obtained in the embodiment 1
or the embodiment 2 (as described above, Table 8 and Table 9 relate
to the wireless multi-hop network different from that to which
Table 1 to Table 7 relate).
[0153] The average hop-number calculation section 26 calculates the
number of hops of each relay node installation point candidate in
each relay node installation point candidate set. In Table 8 and
Table 9, let's assume that the number of hops of the node 2 is 2,
the number of hops of the node 3 is 2, and the number of hops of
the node 4 is 3. Further, let's assume that the relay node
installation point candidate A enables a connection to the base
station via the isolated node 8 and the relay node B and the number
of hops is 5. Furthermore, let's assume that the relay node
installation point candidate F enables a connection to the base
station via the isolated node 5 and the relay node D and the number
of hops is 4. Then, the average number of hops is (5+3+2+2)/4=3 in
Table 8 and (4+3+2+2)/4=2.75 in Table 9. Therefore, the selection
processing section 22 selects the relay node installation point
candidate set in Table 9.
Other Embodiments
[0154] The relay node installation point selection device 2 may
work as one function of the base station. At this time, the base
station has both the function of diagnosing the node-to-node
connectability and the function of selecting the relay node
installation point. In this case, insertion of the node-to-node
connectability diagnosis between the selection processes of the
relay node installation point may raise the possibility of further
reducing the number of relay nodes. This is because there may be a
case where a direct connection between the isolated nodes becomes
possible.
[0155] Further, it may be possible to connect the relay node
installation point selection device 2 (including the case of being
included in the base station) and the wireless device having a
function of detecting the node connectable in one hop arranged at
the base station and/or the relay node installation point candidate
via a wired network so that the input section 21 of the relay node
installation point selection device 2 receives the node-to-node
connectability diagnosis result and the detection result of the
node connectable in one hop at the relay node installation point
candidate via a wired network. In this case, it may be possible for
the relay node installation point selection device 2 to carry out
the node-to-node connectability diagnosis and the detection of the
node connectable in one hop by controlling the base station and/or
the wireless device.
[0156] Furthermore, when the isolated node group has one or plural
identical broadcasting domains, it may be possible only to carry
out the process in the embodiments described above for one isolated
node for each identical broadcasting domain.
[0157] It may be possible to realize the relay node installation
point selection device 2 of the present invention by storing a
program for realizing the function thereof in a computer-readable
recording medium, and causing a computer, which will serve as the
relay node installation point selection device 2 of the present
invention, to load the program stored in the recording medium for
execution in addition to realizing the function using dedicated
hardware. The so-called computer-readable recording media include
recoding media such as a floppy disk, a magneto-optic disk, and a
CD-ROM, and a storage device such as a hard disk device built in a
computer system. Further, the so-called computer-readable recording
media include one for dynamically holding a program for a brief
time in such a case of transmitting a program over the Internet
(transmission media or transmission waves) or one for holding a
program for a predetermined period of time, for example, a volatile
memory within a computer system.
[0158] While this invention has been described in connection with
certain exemplary embodiments, it is to be understood that the
subject matter encompassed by way of this invention is not be
limited to those specific embodiments. On the contrary, it is
intended for the subject matter of the invention to include all
alternatives, modification and equivalents as can be included with
the sprit and scope of the following claims. Further, the
inventor's intent is to retain all equivalents even if the claims
are amended during prosecution.
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